The field of the invention relates generally to an offline code validation tool, and more specifically, to a method and system for simulating a selected portion of control logic.
Distributed process control systems, like those used in chemical, petroleum or other processes, typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure, level and flow rate sensors), are located within the process environment and perform process functions such as opening or closing valves, measuring process parameters, etc. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices and execute a controller application that runs, for example, different control modules which make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices. The control modules in the controller send the control signals over the communication lines to the field devices to thereby control the operation of the process.
Information from the field devices and the controller is usually made available over a data highway to one or more other hardware devices, such as operator workstations, personal computers, data historians, report generators, centralized databases, etc., typically placed in control rooms or other locations away from the harsher plant environment. These hardware devices run applications that may, for example, enable an operator to perform functions with respect to the process, such as changing settings of the process control routine, modifying the operation of the control modules within the controller or the field devices, viewing the current state of the process, viewing alarms generated by field devices and controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, keeping and updating a configuration database, etc.
During commissioning and/or maintenance of process plants, users routinely make modifications to control logic of the process controllers while the process controller is online, that is, while the process controller is actively controlling a process, because validation of the intended modification is not possible until the control logic code is downloaded onto the process controller and then is permitted to act on the process. However, placing the untested control logic changes into service can yield unpredictable results.